CMB Holed piston Fix

[Tom Foley]

Lots of guys have" holed " the junk TOO THIN CMB pistons due to abnormal combustion and the fact that the piston dome between the dished dome and the overmilling underneath create a dome that is flat out too thin . Well Mike costanzo gave me his to try and fix and I am happy to report that the process has worked flawlessly and we are now awaiting field testing . I made a heat sink /grounding /clamp fixture to do this and it worked great . I did not try to replicate the dish in the dome 100 % but did blend in the area welded after trimming on the lathe . The resulting weld sink on the underside of the dome in the area that was " Holed " is now 3 times thicker than it was and does not require any machining to clear the rod upper end .

 

[julianconde]

your awesome Tom you Rock

julian

 

[NITROSNIFER]

Is the beer for cooling while welding or better as a cutting fluid???

 

[Wally Marsh]

There you go Pork Chop Pete, send your 101's to Tom and see if this would be a good fix. More oil and a fatter needle wouldn't hurt, either.

Wallster

 

[Tom Foley]

Is the beer for cooling while welding or better as a cutting fluid???

Just a mild celebration ..for some humor ! :lol:

 

[dwilfong]

Is the beer for cooling while welding or better as a cutting fluid???

Just a mild celebration ..for some humor ! :lol:

I think the beer was to calm the nerves before pushing the peddle. :lol:

I got one you can test on to.

David

 

[Tom Foley]

Is the beer for cooling while welding or better as a cutting fluid???

Just a mild celebration ..for some humor ! :lol:

I think the beer was to calm the nerves before pushing the peddle. :lol:

I got one you can test on to.

David

Testing is over ....as long as these pistons are made like this i should stay busy !! I just cant figure why they would change proven designs unless trying to sell more parts ..but this deal is just FUBAR !! I would maybe buy one ..but after that I would be done . Offering this service for 50.00 if anyone is interested .

 

[dave roach]

Tom

Are you a Certified welder.Looks like it by the glob on top,I would have left the weld on top of the piston.LOL-LOL-LOL

Dave Roach

 

[Michael Costanzo]

There you go Pork Chop Pete, send your 101's to Tom and see if this would be a good fix. More oil and a fatter needle wouldn't hurt, either.

Wallster

wally, this had nothing to do with more oil and fatter needle. this is called "the junk" that cmb has the balls to sell for this kind of $$$! :angry: have ran cmb and EVERY type of engine on the market and never have done this to a motor!! hopefully that the newer pistons don't have the dome,this crap will stop!.A BIG THANKS TO MY BUDDY.."BADDA BING" FOR THE GREAT FIXER.UPPER.(our friend jack o'mally)would have been proud! hopefully in a few weeks i will get back to all of you with the results. mike.

 

[FloridaScaleBoater]

Is the beer for cooling while welding or better as a cutting fluid???

It is to only lubricate the machinest

 

[Keith Wicks]

Nice work you have done there. Having seen pistons out of racecar engines I would say it was caused by being to thin and a way to lean condition. Keep up the good work.

 

[Joe Warren]

After about 100000 zillion laps with RS101`s & 9 different engines total... I have only burned 1 piston. It was on a 110 degree heat index day & a new busted header coupler caused my problem, I put the header pipe on with brake cleaner to help the fit, Then brake cleaner attacked the rubber & We lean on Them Ever Time with some BIG props...... it is a learning curve & most F class boaters learned it with the K90`s A big engine Needs fuel to Run Fast & Live. Being Nitro is a Oxygen bearing Fuel(greatly effected by compression ratios) Head Bowl & compression Must be Correct. Obstructed needle valve (TRASH) leans motors Down too, Restricted pipe pressure fittings lean engines down, Over cooling a RS engine requires you to Squeeze the piss out of the Needle while the engine is trying to make heat, Boat Set up too tight Loads any engine to death,Too much Prop load, Wrong pipe, Restrictive muffled incorrect pipe,Burnt header couplers, The RS engine has about 4 times too much water flowing thru it Even on a hot day. The Piston Is the part that will fail Finally. But a closer look you could fine the REAL PROBLEM WITHIN the BOAT............. p.s. If you Blame the piston & Never Find the Real Problem?? You will never fix the problem. FRANKIE, I would bet someone could built those same pistons out of CAST IRON? Learn the flow meter & some relative numbers to apply to your set up & your stk pistons will live....... Tom I give you a E again for Effort. The sxit you try is Amazing!! Do you have this same problem Tom with your Personal CMB engines? Mike, Who set your engine up? Do you have a way to measure bowl volume & head clearence? WE the boater are modifying the Engine to Drink 50-60-65 Percent Nitro.. it does not come that way... & there some RISK involved & yes it can Get Very Expensive.

 

[Michael Costanzo]

Nice work you have done there. Having seen pistons out of racecar engines I would say it was caused by being to thin and a way to lean condition. Keep up the good work.

good eyes,yes,very thin piston dome and went lean because of a blown header coupler.

 

[Michael Costanzo]

After about 100000 zillion laps with RS101`s & 9 different engines total... I have only burned 1 piston. It was on a 110 degree heat index day & I lean on Them Ever Time with some BIG props...... it is a learning curve & most F class boaters learned it with the K90`s A big engine Needs fuel to Run Fast & Live. Being Nitro is a Oxygen bearing Fuel(greatly effected by compression ratios) Head Bowl & compression Must be Correct. Obstructed needle valve (TRASH) leans motors Down too, Restricted pipe pressure fittings lean engines down, Over cooling a RS engine requires you to Squeeze the piss out of the Needle, Boat Set up too tight Loads any engine to death,Too much Prop load, Wrong pipe, Restrictive muffled incorrect pipe, The RS engine has about 4 times too much water flowing thru it Even on a hot day. The Piston Is the part that will fail Finally. But a closer look you could fine the REAL PROBLEM WITHIN the BOAT............. p.s. If you Blame the piston & Never Find the Real Problem?? You will never fix the problem. FRANKIE, I would bet someone could built those same pistons out of CAST IRON? Learn the flow meter & some relative numbers to apply to your set up & your stk pistons will live....... Tom I give you a E again for Effort. The sxit you try is Amazing!! Do you have this same problem Tom with your Personal CMB engines?

hi joe, learned with my first p/s in this motor about the water cooling problem,i fixed that with closing of the lower section,also have learned about proper comb chamber size and VOLUME,i also relized after that i had tried to sqeeze it down to .010,should have left it at .014.boat was very wet(tried lifting stut)went to much.motor is going back in a rigger. i am in no way a nubie to this hobby or nitro! i have never seen a motor do what these newer cmb's do. years ago you could try just about ANYTHING to a motor and it might pepper the piston or burn a plug,and that was it.i have learned A TREMENDOUS AMOUNT since signing onto this site, buying marty's program,and a BIG thanks to dave wilfong for opening my eye's and mind to what needs to be done to get them to work better.i have won nat's and div's back in the day with stock and slightly modded motors.now the game has changed and i wish i had more time to test stuff out,but this is a secondary hobby for me(joe, if you think this hobby is expensive..try building 2,000+horsepwer and the car to handle it) but i enjoy it as much as possible and like hanging out with friend's and smelling nitro! hopefully i can spend some quality time learning and having fun.mikie.

 

[Joe Warren]

Nice work you have done there. Having seen pistons out of racecar engines I would say it was caused by being to thin and a way to lean condition. Keep up the good work.

good eyes,yes,very thin piston dome and went lean because of a blown header coupler.

Mike your lucky to know Tom he would try to Weld a Bananna Pealing to a Broom Stick? He just needs to figue out what gas is Needed. :huh: :blink: B)

 

[Michael Costanzo]

Nice work you have done there. Having seen pistons out of racecar engines I would say it was caused by being to thin and a way to lean condition. Keep up the good work.

good eyes,yes,very thin piston dome and went lean because of a blown header coupler.

Mike you lucky to know Tom he would try to Weld a Bananna Pealing to a Broom Stick? He just needs to figue out what gas is Needed. :huh: :blink: B)

joe, that is soo true, i know tommy from back in the day of racing motorcycle's up in ny.he is like me, i will try ever angle to fix something.we have been talking about this fix since it happened.i love cmb because they are for the most part bullet proof.just dissapointed alittle with some of the nonsense,but this is part of racing and deffinatly part of NITRO!!, but this is what has keeped me interested in all nitro(sorry not gas)things for over 30 years and probably will do it till i die!

 

[Joe Warren]

Mike there are so many things that effect the Piston burn Pattern. Many mfgers are using a secret Recipe of silicone & alloy blends to make the parts today. the Big engine are Harder to get them to Run Hard & Stay cool & Happy. But the plug element tells all. If the engine is set up correctly? The White packing in the plug stays White for several runs,The Wire color is the fuel mixture ( the wire Does Not lie. Believe what is says )The color of the ring around the plug is the Load that the engine is operating under.This can be Prop or Boat set up. Now if a header coupler was the fault of the piston failure, I`am sure you know you were sucking raw air with No fuel back thru the exhaust. All Big engines Eat Throw Away Parts. You got to stay on them. The higher the percentage nitro the More heat & stress you can occur. If you are Reading the Plug condition you will always know what direction you can go to increase the Speed & Performance. Its the Only thing I want to see when the boat come back in........ You know the third channel is a funny thing. You are tuning by EAR to get the engine to clean out on the pipe. But you just may be flowing a extremely High Flow Number when it happens???? If this Happens You have a problem... Either the engine is not set up correctly,Pipe too big or long,Excessive bowl volume, Exccesive head clearence, wrong prop. I always want to know what the flow number is just as the engine comes into a Good needle & I come into the Good needle from the rich side setting.. Bring the boat in & see what the Flow Meter Says?? 70 degree day most of the Big engines will flow under 40 or under on a (BORIS) Blood pressure type flow meter. AS the temps rise & the quality of air changes your flow number will change. But you need a base line......

 

[Piston1]

I once saw a fellow try to fix a worn out head button using JB Weld, and try to refit a piston using soft plating. The solution is in the head button. It can be fixed using primitive tools.

 

[Tim_Duggan]

The color of the ring around the plug is the Load that the engine is operating under. This can be Prop or Boat set up.

Joe,

what do you look for on this area - can you explain in a little more detail please? For example - what does this area show exactly when there isn't enough load on the engine?

Tim

 

[Tom Foley]

Joe , undoubtedly conditions were not right for this to happen . The real point is in this hobby things like blown couplers etc will always happen (unless you use my sleeve over pipe/header mod ) and pistons never used to be this thin to my knowledge . I have had many CMBs and never had this happen till recently but I may be wrong . Anyway the **** dome is too thin !! Lots of other areas to take weight out of the piston . Look at the Mac 84 piston under the dome , the casting is convex and not milled flat to square up the wrist pin boss area for clearance . The thicker cast material is left in . Made by the same company you wonder why the backward thinking unless to sell more parts ? Well lets see whats out there and see if we can't fix some of thses and save all that sleeve work that has been done . Hopefully we can get these pistons fixed .

BTW anyone who does not want to try this and would like to donate them to SCIENCE :lol: :lol: let me know and I will pay postage as long as the rest of the liner and piston is good .